Computer Numerical Control

INTRODUCTION
CNC is an acronym for (Computer Numerical Control), topics
covered here include, Programming, Mechanics, and Design; with a CNC if
you can think of a task, you can automate it, many things are controlled
numerically today.

Before CNC it was NC (1940s and 1950s) which stands for numerical control,
different from today mainly because of the invention and evolution of IC's
(Integrated Circuits).

The Arduino is one very
good example of a Micro-Controller with some very interesting IC's, it has an Atmel chip that functions as a processor and it can store
code, the Arduino board also has an FTDI integrated circuit for USB connection.

MODERN CNC APPLICATIONS

Rapid Prototyping.

Safety/ Removal and View
of Objects that may Harm or Destroy Life.

Repetitive
Manufacturing.

Industrial Automation.

Hobby

CNC'd devices of today include
Drones, Autonomous Robots, SLS and Filament 3D-printers, and a large number of
different Cutting machines, Pick and place machines for building circuits, some
of these machines do jobs humans should not and can not do, even
Vending machines are CNC'd.

Computers today are getting
smaller and smaller, but still faster and faster; for example a micro-controller
called Arduino can run a 3D-Printer, and the same Integrated Circuit that powers
the Arduino also powers a
micro sized Computer called the
Raspberry PI; Intel
even has something small, Intel competing with ARM now has a
mini Computer
called the Galilao, a 512MHz
dual core Credit card sized computer, and yes others can be found.

Stunning advancements are taking
place every day because of SMD (Surface Mount Design) Electronic Components,
these Components make the
computers and controllers much smaller; the ideas
generated by driven people with problems, along with new technology like the
3D-Printer make new advancements available to more and more people everyday.

Comprehension of a
CNC.

To help understand what a CNC machine is, let's take a look at a Scroll Saw! As
you probably know, a Scroll Saw is a Bench Top, manual Machine used to cut
detailed parts out of a chosen material, this material is usually Wood but
sometimes Plastic, Aluminium, or in very rare cases Mild-Steel, accuracy is
sometimes very difficult to achieve with this tool .

To use the Scroll-Saw an Operator has to move the part over a bed and follow a
line with precision, one slip and that's it for that part (in most cases), or a
blade can break; the more detailed the part, the more risk a slip may happen and
all the time spent will be lost by damaging the part, the Scroll-Saw also cuts
in 2-D, so profiling is another added factor.

Imagine a Scroll-Saw but instead of a blade oscillating up and down, we have a
rotary cutting tool like a Drill-bit, the bed has some clamps to hold the part
for you but it moves right to left, forward and backward, the bit can move up
and down into the work, this machine would now be called a Milling-Machine.

A Milling-Machine/ Engraver/ Tangential Cutter/ Router/ Plotter, are all devices
that move on three or more planes or motion, these machines can cut/ move into
the work over a number passes, they can move a tool off the bed incrementally,
move a Gantry, and
move the bed on two plains incrementally to create a profile.

With a CNC'd machine and Automation, any part can be cut and profiled accurately
by giving the proper command to some motors that are attached to a machine; an
ATC (Automatic Tool Change) will select the proper Cutting Tool/Bit, PWM (Pulse
Width Modulation) changes the spindle (Shank) speed, Motor Drivers control motor
position and speed, and the Computer runs some algorithms to take care of
feed-rates so no tool gets injured on the job.

DIFFERENT TYPES OF CNC
MACHINES AND FUNCTIONS
Not all machines are created equal, some interface in different ways, some Cut
material, some Print material and create 3D-Objects, some are Robotic-Arms and
are used to assemble things, Pick and Place machines assemble PCB/PBA's
(Printed-Circuit-Boards/ Printed Board Assemblies) by the thousands, even
millions per day.

CNC is used widely today in manufacturing for many different reasons, the
following are some of the important fields where the manufacturing processes has
improved greatly and continues to improve today:

Material Removal:

Machines that perform Drilling operations, Boring, Tapping, Reaming, and Counter
tapping, are classed in this category, in addition to turning operations other
Material Removal applications include Facing, Knurling, Threading, and
Pocketing.

Grinding operations such as ID (Internal Diameter) Grinding and OD (Outside
Diameter) are also carried out using Material Removal machines, Contour grinding
was an operation that couldn't be done until CNC technology came into play.

An example of where a Material Removal Machine might be used can be found in the
Sheet Metal industry where thin sheets of metal is used to produce Cabinets or
even a Car Body; holes are drilled at specific locations (Removal of Material),
the sheets are then bent and folded to fabricate various finished shapes with
varying strengths.

The filing cabinet as noted is an example, in order to fabricate one a CNC aided
machines cut sheets of thin steel using Water, Laser cutters, or Plasma cutters,
then a Drill press is used for the holes, they are drilled very precisely in
predetermined places, finally the sheet is bent to a specific shape and
assembled using a Robotic Arm.

Electrical Discharge Machines (Plasma), Machines work by removing metal with
electricity, some even call the process "burning the metal" but
that's not the case, these machines come in two forms.

The Wood Working Industry:

The same way CNC
machines are being used in the metal removal industry they are also used in the
wood working industry, Drilling and Routing are the two most common CNC
operations that are being carried out in this industry.
There are wood working machines that are able to carry out any number of other
operations by the use of ATC (Automatic Tool Change) devices, and machines with
many axis.

There are various types of
engraving machines that use CNC technology, Water jet CNC cutting machines that
use Water Streams at very high pressure cuts material, some other CNC machines
are used for the manufacture of electrical components, for example a Coil
winders, Wire stripper, or advanced Pick and Place machines.

Prototyping:

Research and development is pricy business, one off items are very expensive for
a wide range of reasons, from material costs being high from not buying in bulk,
to investing in tooling and the manufacture of some not so common if not never
invented parts, this is why people and companies are investing in, even building 3D-Printers.

CNC COMPONENTS
INTRODUCTION:
For use or construction of a CNC machine, it's a good idea to
understand what all the different components are, and how they work together,
similar to owning a Car; the operator should know how to use it's features, for
example turn on the Windshield wipers, turn the lights on, place the car/ truck
in gear. Having a good understanding of what's happening under the hood is a
good idea also, when you know your machine in and out, you'll be more safe,
comfortable, just simply able to get the best out of it.

In order to learn about a particular machine the best thing you could do is to
refer to its manual, the manual provides information about the internal parts,
it lists specifications such as its maximum values in terms of power
consumption, speed, cutting limits, if the machine has an ATC (automatic tool
changer) the number of cutting tools it is able to hold, and more.

Knowing what makes up a CNC
Machine is helpful if you want to build your own, or if you want to modify a
manual machine. The conventional 3-axis machine is the most common for the Do It
Yourself project, the 3-Axis machine can be used for 3D-Printing, Laser-Cutting,
Spindle-Cutting (milling), Tangential-Cutting, Plasma/ Torch-Cutting, Waterjet-Cutting,
or Hotwire-Cutting.

People who assemble their own
machines at home often have great success, the online community is very large so
support is just around the corner, the components required are few, some
technical know how is needed (online community) so some reading,
troubleshooting, and parts hunting, will be needed to complete this rewarding
project.

The best part, after building
your own machine, you'll have that extra know how for other complicated
projects, and you'll have the machines to help get those complicated projects
finished with extreme accuracy, besides all that, it's easier than one might
think, everyone has a hidden skill or two.

In case you decide to perform
some modifications to an existing conventional machine some things will need to
be determined before it can be converted, like Motor size, the proper Driver for
that Motor, the proper Power supply/ supplies for the motor(s), even the kind of
motor and driver you want to use, Steppers are common but DC, Servo, or
AC-Motors can be used with the proper Driver.

Mechanical Breakdown:

Motors:

Stepper

Servo

DC

AC

Universal

Motors vary, so do the drivers and controllers, the Parallel Driver (DB25
interface) is a common driver for Stepper-Driven machines, Serial Drivers
(RS232, USB) Arduino, Gecko, are often used for Servo, DC, Universal and AC
motors.

PWM circuits containing TRIAC's with a Micro Controller interfaced via
Serial-Port are used to control AC-Motors, and Universal motors can be
controlled using any PWM circuit with a Micro-Controller (Serial-Port
Communication), an Encoder is used with these motors making a Closed-Loop system
for high Accuracy.

Slides/ Drive Screws/
Belts:

The Drive Screw for the CNC
consists of some threaded bar stock; known as Ready-Rod, this stock can be found
down the Hardware Isle at the local hardware store, good for a small desktop
hobby machines. ACME rod is used for industrial applications because of the
thread pitch, the coarser the pitch the faster the machine can move with little
motor movement, the Nut for industrial machines has anti-backlash properties, a
simple spring also used in the Open-Source 3D-Printer builds is used in
conjunction with the Nut.

Belts are also used on some
applications, but not common for cutting machines due to torque loss and belt
stretching, belts also make for a fast moving machine, hence why Belts are used
on the common Open-Source 3D-printers where little resistance is placed on any
axis and speed is required.

Bearings/
Bushings:

Linear Slide Bearings:

Bushings:

Other (V-Groove, ZZ, ULN):

Controllers:
Controllers interface between the motor-drivers and your
Computer. It is not impossible to design and construct your own controller board
plans can even be found on the web or included with some PCB/ PBA (Printed
Circuit Board/ Printed Board Assembly) design software, for example "Eagle".

As noted above, the controller
will interface with the PC in different ways, a Serial-Controller will have
Firmware installed, a
Parallel-Controller will connect directly to the
Motor-Drivers, one being much easier than the other to configure.

A Serial connection:

Firmware is loaded onto
Arduino this is known as a Sketch, information is sent from the computer in
the form of a packet to the Arduino,
Arduino processes Packets of information
based on the instructions written in the Sketch, and electrical Pulses are
sent to move the Motor.

The Computer sends electrical
pulses directly threw the Parallel-Port to Motor-Drivers that move the Motors.

In addition to
the Motors, the Bearings,
Controller, and Power-Supply, the CNC machine also may
carry some accessories, among them could be probing systems, pallet changers for
automatic removal and reloading of material, adaptive control systems
(temperature sensing for example), and other automation systems, the list of
accessories could be a very long one.

In the case these accessories are
included with a Machine you purchased, details can found in the user manual, if
they are aftermarket additions other manuals/ datasheets should be available
online.

CNC Software:
When it comes to running a machine with the help of CNC software
three components are required:

CAD (computer aided design), CAD software is used to draft a part or complete
assembly using the computer.

CAM (Computer Aided Manufacturing) is software that programs the machine and
plans the cut operation, this software converts the CAD drawing into G code,

Machine Software (compiler), this is the software that converts the G-Code into
packets or pulses to control the machine.

Software packages
or components can be found online, this website offers Machine-Software for sale
with Serial or Parallel control, configuration required for use with some
machines, some Drivers are already configured just select the appropriate
configuration file.

Spindle direction, speed of the tooling, and coolant changes are some of the
things some machines can't be programmed to monitor, in this case the operator
has to manually monitor and control these features.

When it comes to
programmable functions they vary from machine to machine. Also the commands used
for changing them also vary from one manufacturer to another, Post-Processors
can be written for CAM software so the outputted G-Code will work with your
machine, M codes (miscellaneous commands) are included with the Post-Processor.

COLLECTING PARTS

Salvaging parts from old electronic devices and toys are great ways to start
collecting components and get started if you're a Do-It-Yourselfer and you want
to build your own machine. Alternately buying the parts isn't a bad idea either,
specially if there's a concern a part or two salvaged won't work properly, or at
all.

Collecting a part or two from an
old device can be easy... Just smash your way in with a hammer and collect the
parts you want, or analyse the construction and learn from it while taking it
apart.

Old Printers are a good source
for parts, and Motors, depending on the kind of printer Stepper, Servo, or DC,
motors will be found in Printers, the Dot-Matrix machines have Stepper-Motors.
It's important to consider voltage and amperage values.

BENEFITS OFFERED BY CNC
TECHNOLOGY TODAY
Save Time! Save labour! Save Material! Produce goods when
you're someplace else, make money at home when you're at work. R&D, and
concepts, prove your idea in hours not weeks or months, save on material by
having less error.

The following are some of the
advantages:

Safety

CNC machines do the dirtywork,

Superior Automation
If a CNC machine is working properly there's no real need
for an operator, the machine can load new parts even package finished ones, just
keep providing enough raw materials for the machine to keep running, if the
needs of the machine are taken care of it could run uninterrupted for days, even
weeks, that way the operator can attend to other important things, since the
machine is automated and computer controlled the accuracy of produced parts are
of a very high level.

Since the machine is driven by software the operator doesn't have to be a
skilled craftsman, even if a CNC workshop has several machines, having just one
supervisor is enough to manage high production levels, saving on
labour.

Flexibility
When you use a CNC machine you have the option of making a wide
range of different products without any problems, it's as easy as changing the
program, often this program is a simple text file that can be used time and time
again to produce the exact same part, time after time.

Since CNC
machines could be adjusted to manufacture different products in short times it's
not necessary to have a big inventory, but not a big deal if you do either,
machine set up is usually pretty simple, jigs help with complex setups,
production runs for new product can be started in limited time, often a new part
can be planned, programmed, and produced in one day.

Modern CNC
machines are developed so well that they never need an operator to work, they
can be controlled over the web, in cases where raw material has run out, the
machine runs out of oil, or in case of a break down, the machine will send an
alert to the operators mobile phone for attendance.

DISADVANTAGES OF CNC
MACHINESCosts:
CNC machines are generally more expensive than manually operated
machines, however costs are offset by production levels and quality, prices are
also coming down, do it yourself builds are inexpensive but still result in high
quality production.

Software is expensive for the most part, MasterCAM and others can cost into the
thousands of dollars, Solidworks for example could cost as much as ten thousand
dollars, machine software often comes with proprietary machines but may not,
some Machine software can be found free online (EMC), however Windows versions
cost money (Mach3).

Employment:

Because CNC
machines need fewer operators (one operator could look after a number of
machines) it contributes to unemployment and deflation of goods, however
maintenance people still need to be employed to keep these machines working, and
replacement parts still need to be built by someone.

Education:

The form of
education has changed, with CNC's the present day school curriculum may not
include training on manually operated machines, this limits new grads to
Computer controlled machines, they may not have the same skill as past
graduates, the computer does all the manual work for them.

When you weigh
advantages against disadvantages of the CNC machine however, it appears to me
that the advantages may outweigh the disadvantages, therefore, the CNC machine
is not only going to stay but also develop further in the future.

HISTORY

After the 1970s when computers
made their appearance, Conventional and Numerical Control systems were modified
for Computer Control, instead of running off a special punched Tape, today
Machines are controlled from a file generated from a Computer mathematically.

Today, an Operator has to sit near the machine to monitor the progress and
interrupt the process in case anything goes wrong, and the Operator loads the
raw material, opposed to physically producing the first example, setting up the
machine, loading the raw material, and monitoring/ controlling the machine.